1. Field of the Invention
The present invention relates to a light emitting device drive controller and a light emitting device driving apparatus that are suitable to check a changing state of a predetermined factor (e.g., a remaining amount level of a voltage value of a battery) with an ON/OFF state of a light emitting device.
2. Description of the Related Art
A portable electronic device (e.g., notebook personal computer) is equipped with a battery and is supplied with power from the battery to operate. The power supply capacity from the battery is reduced as the electronic device is utilized by a user and will not be able to supply power at a level that can operate the electronic device normally over time. During the course of the normal operation of the electronic device, if the battery cannot supply power that can operate the electronic device normally, the electronic device stops operation that should be performed under normal circumstances or operates improperly. To solve such inconveniences, technologies are disclosed for checking a remaining amount level of a voltage value of a battery (a changing state of a predetermined factor) (e.g., Japanese Patent Application Laid-Open Publication No. 2004-14228). It is known that technologies for checking a state of a battery include a technology for calculating a remaining usable time of a battery for numerical display on a display and a technology for performing indicator display of a remaining amount level of a battery. For example, a plurality of LEDs is applied to the latter indicator display technology. The plurality of LEDs is provided on, for example, a portion of a battery pack mounted to the electronic device in the shape of an indicator (aligned in a line).
Description will be made of an example of the indicator display technology using LEDs with reference to FIG. 12 and FIG. 13. FIG. 12 is a circuit block diagram of an example of a conventional light emitting device driving apparatus. In FIG. 12, five LEDs 1 to 5 (light emitting devices) are driven selectively and statically. FIG. 13 is a circuit block diagram of another example of a conventional light emitting device driving apparatus. In FIG. 13, five LEDs 101 to 105 (light emitting devices) are driven selectively and dynamically. In FIG. 13, the same numbers are added to the same components as FIG. 12 and the description thereof will not be made.
<<Static Drive Type Light Emitting Device Driving Apparatus>>
In FIG. 12, a battery remaining amount detecting unit 13 detects a remaining amount (currently charged voltage value) of a battery 14 mounted for operating an electronic device to the electronic device. For example, the battery remaining amount detecting unit 13 detects the remaining amount of the battery 14 periodically at predetermined time intervals and outputs the detected remaining amount as binarized battery remaining amount data. That is, the battery remaining amount data are updated at predetermined time intervals.
A microcomputer 6 performs static drive to turn on/off any of the five LEDs 1 to 5 selectively based on the battery remaining amount data supplied from the external battery remaining amount detecting unit 13. That is, the microcomputer 6 divides the remaining amount range of the battery 14 into five ranges from an empty state to a fully charged state and if the remaining amount of the battery 14 is less than ⅕, only the LED 1 is turned on; if the remaining amount of the battery 14 is ⅕ or greater and less than ⅖, the LEDs 1, 2 are turned on; if the remaining amount of the battery 14 is ⅖ or greater and less than ⅗, the LEDs 1 to 3 are turned on; if the remaining amount of the battery 14 is ⅗ or greater and less than ⅘, the LEDs 1 to 4 are turned on; and if the remaining amount of the battery 14 is ⅘ or greater, all the LEDs 1 to 5 are turned on. An anode of each LED 1 to 5 is connected to a power supply voltage port VDD of the microcomputer 6 via a limiting resistor 7 to 11 to limit the current of the LED 1 to 5. On the other hand, a cathode of each LED 1 to 5 is connected to a control port C1 to C5 for turning on/off the LED 1 to 5. A switch 12 for checking the remaining amount of the battery 14 is connected between the power supply voltage port VDD and a control port C6. The switch 12 is operated when a user checks the remaining amount of the battery 14 and is configured to be closed (ON) only during the operation and to be opened (OFF) when not operated. The control port C6 is grounded via a resistor 15 on the outside of the microcomputer 6 (or may be grounded within the microcomputer 6). The control port C6 is a port that is pulled down to low level within the microcomputer 6 when the switch 12 is off (opened).
When the switch 12 is operated (to be the closed state) to check the remaining amount of the battery 14, the control port C6 of the microcomputer 6 is pulled up to a voltage level of the power supply voltage port VDD and is changed from low level to high level. The microcomputer 6 detects that the control port C6 is changed to high level and the detection result is used as an interruption request to start execution of a program for performing the LED display of the remaining amount level of the battery 14.
First, the microcomputer 6 acquires the battery remaining amount data detected in the battery remaining amount detecting unit 13. The microcomputer 6 then finds out which LED of the LEDs 1 to 5 is instructed to be turned on by the battery remaining amount data in accordance with an arithmetic processing program. For example, if the remaining amount of the battery 14 is ⅖ or greater and less than ⅗, this content instructs to turn on the LEDs 1 to 3. In this case, the microcomputer 6 sets the control ports C1, C2, and C3 to low level and sets the control ports C4 and C5 to high level. In this way, the LEDs 1 to 3 are turned on for a time period determined by the program of the microcomputer 6, and the user can learn that the remaining amount of the battery 14 is ⅖ or greater and less than ⅗.
If the remaining amount of the battery 14 is other than the above description, any LEDs 1 to 5 can be turned on correspondingly to the remaining amount of the battery 14 by changing the levels of the control ports C1 to C5 correspondingly to the battery remaining amount data.
<<Dynamic Drive Type Light Emitting Device Driving Apparatus>>
In FIG. 13, a microcomputer 106 performs dynamic drive to turn on/off any of the five LEDs 101 to 105 selectively based on the battery remaining amount data supplied from the external battery remaining amount detecting unit 13. That is, the microcomputer 106 divides the remaining amount range of the battery 14 into five ranges from an empty state to a fully charged state and if the remaining amount of the battery 14 is less than ⅕, only the LED 101 is turned on; if the remaining amount of the battery 14 is ⅕ or greater and less than ⅖, the LEDs 101, 102 are turned on; if the remaining amount of the battery 14 is ⅖ or greater and less than ⅗, the LEDs 101 to 103 are turned on; if the remaining amount of the battery 14 is ⅗ or greater and less than ⅘, the LEDs 101 to 104 are turned on; and if the remaining amount of the battery 14 is ⅘ or greater, all the LEDs 101 to 105 are turned on. Anodes of the LEDs 101 and 102 are connected to a control port C103 of the microcomputer 106 via a limiting resistor 107 to limit the current of the LEDs 101 and 102. Anodes of the LEDs 103 and 104 are connected to a control port C102 of the microcomputer 106 via a limiting resistor 108 to limit the current of the LEDs 103 and 104. An anode of the LED 105 is connected to a control port C101 of the microcomputer 106 via a limiting resistor 109 to limit the current of the LED 105. On the other hand, cathodes of the LEDs 101, 103, 105 are connected to a control port C104 of the microcomputer 106 and cathodes of the LEDs 102 and 104 are connected to a control port C105 of the microcomputer 106. A switch 110 for checking the remaining amount of the battery 14 is connected between the power supply voltage port VDD and a control port C106. The switch 10 is operated when a user checks the remaining amount of the battery 14 and is configured to be closed (ON) only during the operation and to be opened (OFF) when not operated. The control port C106 is grounded via a resistor 111 on the outside of the microcomputer 6 (or may be grounded within the microcomputer 6). The control port C106 is a port that is pulled down to low level within the microcomputer 6 when the switch 110 is off (opened).
When the switch 110 is operated (to be the closed state) to check the remaining amount of the battery 14, the control port C106 of the microcomputer 106 is pulled up to a voltage level of the power supply voltage port VDD and is changed from low level to high level. The microcomputer 106 detects that the control port C106 is changed to high level and the detection result is used as an interruption request to start execution of a program for performing the LED display of the remaining amount level of the battery 14.
First, the microcomputer 106 acquires the battery remaining amount data detected in the battery remaining amount detecting unit 13. The microcomputer 106 then finds out which LED of the LEDs 101 to 105 is instructed to be turned on by the battery remaining amount data in accordance with the arithmetic processing program. For example, if the remaining amount of the battery 14 is ⅖ or greater and less than ⅗, this content instructs to turn on the LEDs 101 to 103. In this case, the microcomputer 106 sets the control port C103 to high level and sets the control ports C104 and the control ports C102 and C105 to a predetermined frequency (e.g., 100 Hz) as well as to high level and low level, respectively, in a reversed phase. The microcomputer 106 sets the control port C101 to low level. In this way, the LEDs 101, 103 and the LED 102 are turned on and off repeatedly for a time period determined by the program of the microcomputer 6 at respective predetermined frequencies in a complementary manner. For example, if the LED is turned on and off repeatedly at 100 Hz, the LED looks like turned on continuously to the human naked eye. That is, the user can learn that the remaining amount of the battery 14 is ⅖ or greater and less than ⅗.
If the remaining amount of the battery 14 is other than the above description, any LEDs 101 to 105 can be turned on correspondingly to the remaining amount of the battery 14 by changing the levels of the control ports C101 to C105 correspondingly to the battery remaining amount data.
However, in the case of the static drive type light emitting device driving apparatus shown in FIG. 12, the microcomputer 6 must be provided with the number of the control ports corresponding to the number of the LEDs one-on-one (five in the case of FIG. 12). Therefore, the total number of the ports of the microcomputer 6 is increased proportionally to the number of the LEDs and the size of the microcomputer 6 may be enlarged, which is problematic.
On the other hand, in the case of the dynamic drive type light emitting device driving apparatus shown in FIG. 13, the microcomputer 6 must be provided with the number of the control ports for turning on the LEDs, which is a sum of the number of the LEDs (with a common anode) constituting a LED group surrounded by a dotted line and the number of the LED groups (five in the case of FIG. 13). In the dynamic drive type light emitting device driving apparatus, as compared to the static drive type light emitting device driving apparatus, the number of the control ports can be more constrained as the number of the LEDs increases. Specifically, when the total number of the LEDs is six or more, the effect of reducing the number of the control port is exerted on the dynamic drive type light emitting device driving apparatus as compared to the static drive type light emitting device driving apparatus. Otherwise, if the total number of the LEDs is one to three, the number of the control ports of the static drive type light emitting device driving apparatus is less than that of the dynamic drive type light emitting device driving apparatus. If the total number of the LEDs is four or five, the number of the control ports of the static drive type light emitting device driving apparatus is equal to that of the dynamic drive type light emitting device driving apparatus.
By the way, when the indicator display of the remaining amount of the battery 14 is performed with the use of a plurality of LEDs built into the battery pack, the number of the LEDs is typically four or five, for example. However, as described in the light emitting device driving apparatuses of FIGS. 12 and 13, if the total number of the LEDs is four or five, the number of the control ports must be four or five to turn on the LEDs and it is difficult to make the number of the control ports three or less. Therefore, in the light emitting device driving apparatus that controls the lighting of the four or five LEDs, the number of the control ports of the microcomputers 6, 106 cannot be reduced to three or less and it is problematic that the sizes and costs cannot be reduced in the microcomputers 6, 106. The number cannot also be reduced for the wirings connecting a display substrate provided with the LEDs and a substrate provided with the microcomputers 6, 106, and it is problematic that the costs of the apparatus itself cannot be reduced.